The U.S. Center for Disease Control has estimated that each year 2,000,000 hospital-acquired infections burden the United States healthcare economy with over 30 billion dollars in preventable costs. Treatment of bacterial infections with antibiotics is complicated by problems of antibiotic resistance and a slowing pipeline of new antibiotics. The problem is particularly acute for treatment of topical infections. Currently available topical antibiotics are known to leave behind resistant organisms and many biocides are not acceptable for topical use because of their cytotoxicity.
Cationic biocides are a group of antimicrobial compounds that have been in use for surface disinfection and topical applications for the treatment of infection. Cationic biocides are a diverse group of chemical compounds. Typically the antimicrobial action of cationic biocides stems from interaction of the cationic biocide with a microbe's cell envelope. The cationic biocide displaces divalent cations in the cell envelope, which ultimately results in membrane disruption that is lethal to the microbe.
Formulating cationic biocides for topical administration to humans, however, is complicated by the chemical structure of cationic biocides. Cationic biocides are charged, making them highly polar compounds. Although petrolatum is known to have advantageous protective properties when applied to the skin, its hydrophobic nature had previously made it a poor candidate for formulating cationic biocides because of their polar and hydrophilic structure. It was previously thought that an emulsifier would be necessary to disperse a cationic biocide throughout petrolatum. It was also thought that the petrolatum was incapable of delivering compounds such as cationic biocides because the cationic biocide would be trapped within the petrolatum and therefore would be unable to reach and interact with the infecting microbe.
The Applicant has discovered that cationic biocides can be formulated in petrolatum. The petrolatum-based compositions described herein contain nanodroplets of cationic biocides dispersed in the petrolatum. The nanodroplets release the cationic biocides to the application site continuously and have been shown to provide broad spectrum activity against microbes. Additionally, the petrolatum-based compositions described herein are gentle. They do not irritate the skin and are not cytotoxic to mammalian cells. The Applicant has further discovered processes leading to a stable delivery system for a variety of ingredients.